In radiation treatment, doses of radiation delivered via a radiation treatment beam from a source outside a patient's body are delivered to a target region in the body, in order to destroy tumorous cells. Care must be taken to minimize the amount of radiation that is delivered to non-treatment regions while maximizing the amount of radiation delivered to the intended treatment regions. In radiation treatment, a radiation treatment beam aperture shapes the radiation treatment beam to conform, as closely as possible, to the intended target region. The radiation treatment beam aperture is commonly defined by an MLC.